Punchthrough type GTO with buffer layer and homogeneous low efficiency anode structure

A new type of full scale 4.5 kV/3 kA GTO has been developed, fabricated, and electrically characterized. The device utilizes a punchthrough concept with a buffer layer. To avoid the requirement of excessive gate currents for turn-on, the new GTO has a homogeneous anode layer without shorts. The anode has a very low efficiency, which allows efficient extraction of charge during turn-off. With the buffer layer, the new device has a significantly reduced wafer thickness as compared to conventional devices without buffer. This reduces switching as well as on-state losses. The turn-off losses of the best devices were reduced to one third of those of conventional GTOs and, at the same time, the on-state losses were decreased by more than one third.